The present invention relates to a novel process for the preparation of known heterocyclic compounds.
The preparation of unsaturated, heterocyclic compounds by the alkylation of unsubstituted ring substance atoms, which can be carried out, inter alia, in alcohol (EP-A-259 738), is known.
Also known are alkylation reactions in aprotic solvents (EP-A-259 738).
In these cases, subsequent purification of the product is necessary in order to achieve adequate purity, and in addition the yields which can be achieved with the known processes are unsatisfactory.
We have found that compounds of the formula (I) 
in which
R1 is a hydrogen atom or an alkyl group,
A is an ethylene group which may be substituted by alkyl, or a trimethylene group which may be substituted by alkyl,
D is nitro or cyano,
X is an oxygen or sulphur atom or the groups 
xe2x80x83in which
R3 is a hydrogen atom or an alkyl group, and
Z is an optionally substituted 5- or 6-membered heterocyclic group which contains at least two heteroatoms chosen from oxygen, sulphur and nitrogen atoms, or is an optionally substituted 3- or 4-pyridyl group,
are obtained by reacting compounds of the formula (II) 
in which
A, D and X have the meanings given above,
with a base and in the presence of a diluent, and then reacting the reaction mixture with the mixture of CCMP/CMP (2-chloro-5-chloromethylpyridine/2-chloro-5-methylpyridine) with the corresponding hydrochlorides.
Surprisingly, the abovementioned compounds can be prepared in a more simple and fewer process steps and in a better yield by the process according to the invention.
In the general formulae (I) and (II), the variables are as follows:
R1 is preferably hydrogen or a C1-C3-alkyl group, particularly preferably hydrogen;
A is preferably an ethylene or trimethylene group, each of which may be substituted by a C1-C3-alkyl group, particularly preferably an ethylene group;
D is nitro or cyano,
X is preferably an oxygen or sulphur atom or the group 
xe2x80x83particularly preferably an oxygen atom or the group 
Z is preferably a halogenated, 5- or 6-membered heterocyclic group which contains 2 heteroatoms chosen from the group oxygen, sulphur and nitrogen, or is a halogenated 3- or 4-pyridyl group, particularly preferably a halogenated thiazolyl or 3-pyridyl group, very particularly preferably 2-chloropyrid-5-yl.
A very particularly preferred compound of the formula (I) is the compound of the formula (Ia) 
which is obtained by reacting the compound of the formulae (IIa) 
with a base and in the presence of a diluent, and by subsequently reacting the reaction mixture with a mixture of CCMP/CMP with the corresponding hydrochlorides.
A further very particularly preferred compound of the formula (I) is the compound of the formula (Ib) 
which is obtained by reacting the compound of the formula (IIb) 
with a base and in the presence of a diluent, and by subsequently reacting the reaction mixture with a mixture of CCMP/CMP with the corresponding hydrochlorides.
Solvents which can be used are protic and dipolar-aprotic solvents, in particular water, alcohols, ketones (preferably MIBK), esters (preferably butyl acetate), nitriles (preferably acetonitrile, n-propionitrile, butyronitrile), pyridines (preferably CMP), amides (DMF), DMSO or carbonates, or mixtures thereof with water. If alcohols are used as solvents, the compounds of the formula (I) can be obtained directly in a modification advantageous for use as crop protection agents and in the necessary purity.
Examples of alcohols which may be used are:
primary alcohols, such as methanol, ethanol, propanol, butanol, 2-methyl-1-propanol, 1-pentanol, benzyl alcohol,
secondary alcohols, such as isopropanol, sec-butanol, 2-pentanol, tert-alcohols, such as tert-butanol.
Particularly preferred solvents are alcohols which are immiscible or only partially miscible with water (such as n-butanol, amyl alcohol, in particular n-butanol) or nitriles which are immiscible or only partially miscible with water (such as n-propionitrile or butyronitrile, in particular n-propionitrile).
The process may be carried out in the presence of a base. Examples which may be mentioned are: alkali metal and alkaline earth metal hydroxides, such as NaOH, KOH, Ca(OH)2, alkali metal carbonates or hydrogencarbonates, such as Na2CO3, Li2CO3, K2CO3, Cs2CO3 or NaHCO3 and KHCO3. Preference is given to K2CO3, NaOH and KHCO3, in particular K2CO3.
The compounds of the general formula (II) can also be used as alkali metal salt or alkaline earth metal salt in solid or dissolved form.
When working in water, water-alcohol or water-nitrile mixtures, the process is carried out at a pH range between 6 and 13.
Catalysts which can be used are phase transfer catalysts, where appropriate quaternary ammonium halides, such as tetrabutylammonium bromide or chloride, or Cs salts etc.
The reaction can also be carried out by initially introducing the compounds of the general formula (II), optionally as alkali metal or alkaline earth metal salt, and heating them in the presence of a base at temperatures of from 40xc2x0 C. to 130xc2x0 C., optionally under reduced pressure, preferably at 100 to 500 mbar, and then adding the CCMP/CMP mixture at 50 to 90xc2x0 C., optionally under reduced pressure, preferably at 60xc2x0 C. to 80xc2x0 C.
The reaction is expediently carried out under atmospheric pressure, although it is also possible to work under reduced or elevated pressure. Particular preference is given to carrying out the reaction under reduced pressure.
The process is carried out in practice by reacting, for example, 1 mol of a mixture of CCMP/CMP with 0.95 to 3 mol of the compounds of the formula (II), preferably 1.0 to about 2.5 mol, in a solvent such as butanol in the presence of from 1 to 3 mol, preferably 1.5 to 2.5 mol, of a base such as, for example, potassium carbonate and optionally in the presence of a catalyst such as tetrabutylammonium bromide or cesium carbonate.
If water is used in a two-phase system, preference is given to working at pH8-10.
The reaction time is between 3 and 12 hours, preferably 5 to 10 hours. When the reaction is complete, the solvent may be changed if necessary. Here, the majority of the reaction diluent is distilled off under reduced pressure (1-1000 mbar) and the quantity is topped up by one of the abovementioned diluents. Solvent substitution can take place before or after the hydrolysis.
The suspension from the reaction is hydrolysed at a temperature of from 50xc2x0 C. to 100xc2x0 C., and the organic phase is separated off at 50xc2x0 C. to 80xc2x0 C. This phase is cooled, and the precipitated active ingredient is isolated, washed and recrystallized.
The CMP present in the mother liquor (temperature range 50xc2x0 C. to 130xc2x0 C., pressure range 1-1000 mbar) can be recovered and returned to the process: the mother liquor obtained can be admixed with the diluent from the crystallization (1 part of mother liquor/4 parts of solventxe2x80x941 part of mother liquor/0.5 parts of solvent), the suspension is cooled and the precipitated active ingredient is filtered off.
The starting materials of the formula (II) are known and/or can be prepared by processes known per se (cf. JACS 79, (1957), 3565; Arch. Pharm. 305, (1972), 731-736; Heterocycles 31 (1990), 1601-1604; Biosci. Biotechnol. Biochem. 57, (1993), 127-128; Biosci. Biotechnol. Biochem. 56, (1992), 364-365).
The preparation of 2-chloro-5-chloromethylpyridine is carried out analogously to the described process (EP-A-458 109, EP-A-260 485). The 2-chloro-5-methylpyridine is chlorinated in an organic solvent (acetonitrile, carbon tetrachloride, water pH-controlled) using a free-radical initiator (AIBN) at the boil. The conversion of the reaction is terminated at about 40% in order to obtain a high selectivity of 2-chloro-5-chloromethylpyridine. Distillation of the organic solvent under reduced pressure is then carried out.
Following distillation of the solvent, the mixture of CCMP/CMP comprises 5-15% residual solvent, 30-50% CMP and 25-45% CCMP with the corresponding hydrochlorides.
This mixture of 2-chloro-5-methylpyridine and 2-chloro-5-chloromethylpyridine and the corresponding hydrochlorides serves as seed substance for the active ingredient reaction. This mixture can be used in this reaction in undiluted form or in a diluent which is expediently also used in the active ingredient reaction.
The compounds of the formula (I) are, for example, suitable for use as insecticides (EP A2 0235 752, EP A2 0259 738).
The examples below illustrate the subject matter of the invention without limiting it in any way.